Numerical investigation of convective heat transfer enhancement by a combination of vortex generator and in-tube inserts

The application of both the vortex generators and twisted belts were investigated in literature as they are effective in improving heat exchanger thermal performance. In this paper, a novel method to enhance the heat exchanger thermal performances obtained by combining the vortex generator and twisted belt is proposed. The circular tube thermo-hydraulic characteristics were numerically studied by combining the twisted belt and delta wing vortex generators (DWVGs). The effects of twist ratio, attack angles, pitch and vortex generator arrangement were investigated. The emphasis was put on obtaining the optimal parameters. The Reynolds number was based on the hydraulic diameter channel flow, which ranged from 5000 to 25,000. The results indicate that the most favorable vortex generator arrangement is staggered arrangement when the twisted belt twists counter-clockwise. The optimal twist ratio is 4, and PEC increases with the increase in the angle of attack and decrease of the vortex generator pitch. When considering the conditions studied in this paper, the PEC can be improved by 96% similar to 128% compared with the smooth tube. Said improvements are mostly obtained when using the novel combination structures with the staggered arrangement, optimal twist ratio of 4, attack angle of 75 degrees, and pitch of 1.5D.